1987 Other Chevrolet Models Chevy Mallard MOTRHM knocking

I started up my motorhome for the once a month start up, and to transport it to a new location, and it started making a very loud ping or knock. I tied to find the problem and found it was dry of oil, I went to the auto part shop and the man suggested 5w30. The oil cap said 10w30, but I did not feel like it was too big of a deal so I put it in. I ran the engine and it seemed to get better. I drove it about 30 miles and it began to make the noise again, it increased with acceleration, and seemed to not have proper power. It did not ever overheat, and did not reach normal operating temp. The noise stars upon start, and gets louder as it begins to warm.